Measurement of the current-phase relation in Josephson junction rhombi chains

I. M. Pop; K. Hasselbach; O. Buisson; W. Guichard; B. Pannetier; I. Protopopov

doi:10.1103/PhysRevB.78.104504

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Measurement of the current-phase relation in Josephson junction rhombi chains

I. M. Pop, K. Hasselbach, O. Buisson, W. Guichard, B. Pannetier, I. Protopopov

DOI 10.1103/PhysRevB.78.104504 · Physical Review B

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Abstract

We present low-temperature transport measurements in one-dimensional Josephson junctions rhombi chains. We have measured the current-phase relation of a chain of eight rhombi. The junctions are either in the classical phase regime with the Josephson energy much larger than the charging energy, EJ⪢EC, or in the quantum phase regime where EJ/EC≈2. In the strong Josephson coupling regime (EJ⪢EC⪢kBT) we observe a sawtoothlike supercurrent as a function of the phase difference over the chain. The period of the supercurrent oscillations changes abruptly from one flux quantum Φ0 to half the flux quantum Φ0/2 as the rhombi are tuned in the vicinity of full frustration. The main observed features can be understood from the complex energy ground state of the chain. For EJ/EC≈2, we do observe a dramatic suppression and rounding of the switching current dependence which we found to be consistent with the model developed by Matveev et al. [Phys. Rev. Lett. 89, 096802 (2002)] for long Josephson junctions chains.